Straight Turning Operation on Lathe Machine

Lathe machines are used to turn the work straight by making the work rotate about the lathe axis and by feeding the tool parallel to the lathe axis. In the straight turning procedure, a cylindrical surface is produced by the removal of excess metal from the work piece. The job is made to face the ends and drill at the centre and then mounted between the centers with the help of a lathe dog attached to the work piece. For this purpose, a properly ground right-hand turning tool is used. Basically, this tool is clamped on the tool post, ensuring that the overhang is as less as it could be. It is set with its edge that cut almost at the lathe axis or slightly above it. If there is a need for light cuts, the tool needs to be inclined towards the headstock. But for heavy cuts, it needs to be inclined towards the tailstock. After that, the automatic feed is engaged so as to move the carriage to the wished length. Soon, the feed is made to disengage so as to bring back the carriage from where it started. This process is repeated as many times as the job is deemed to be finally finished. Lathe machines are really useful. Apart from them, the demand for other used woodworking machines is also high among the companies engaged in woodworking work of some sort. Pre-owned lot of sheet metal machinery is allowing such companies to achieve better efficiency at lower prices.

Straight Turning

[Read about all lathe operations here]

General.  Straight turning may he performed upon a workpiece supported in a chuck, but the majority of workpieces turned on an engine lathe are turned between centers.  Turning is the removal of metal from the external surface of cylindrical workpieces using various types of cutter toolbit.

Mounting Workpieces. For Straight Turning.Lathe centers must be in good condition and carefully aligned if the turning operation is to be accurate. If necessary, regrind the centers and check their alignment.When turning the workpieces, considerable heat will be generated causing the workpiece to expand. Centers that are too tight may cause binding of the workpiece due to this expansion.The tailstock center or the dead center must be well lubricated to prevent the workpiece from overheating. The center hole and the tailstock center should be lubricated before the cutting operation with a mixture of white lead and motor oil. During the turning operation, feel the dead center frequently to determine whether lubrication or adjustment is necessary.

Proper Cutter. Bits For Straight Turning.Straight turning is accomplished with the left-hand turning cutter bit, the right-hand turning cutter bit, or the round nose turning cutter bit.Wherever possible, the right-hand turning cutter bit or a round nose bit ground for right-to-left turning is used and the hit is fed toward the headstock. If circumstances demand that the bit feed from left to right, such as in turning up to a shoulder, the left-hand cutter bit is used.The round nose turning cutter bit is especially efficient for finishing cuts.

Position of Cutter Bit. For Straight Turning. The cutter bit should be locked in the cutting tool holder and the holder should be fixed to the tool post so that the cutting edge of the bit touches the workpiece surface at about 5 above the horizontal center line of the piece since this position gives the bit a better cutting action. The distance above the center is governed by the diameter of the workpiece and the front clearance angle of the cutter bit. As a general rule, the point of contact of the cutting edge is raised 3/64 inch above the center for each inch of the workpiece diameter.In a horizontal plane, the bit and the holder should be positioned at right angles to the workpiece axis or at a slight leading angle so that the bit will not dig into the workpiece if the bit or the tool holder should accidentally work loose.

POSITION OF THE CUTTER BIT FOR FACING
POSITION OF THE CUTTER BIT FOR FACING

Straight Turning Operation. As a rule, the workpiece is turned down by a number of roughing cuts to a predetermined diameter which is within 1/32 to 1/64 inch of the diameter desired. The remaining metal is removed by a finish cut using a fine fed to produce a good surface. After taking the first roughing cut along the entire workpiece surface check the center alignment by measuring each end with calipers. If the ends are of different diameters, the tailstock center is out of alignment with the headstock spindle and realignment is necessary.Continue cutting after correct alignment is made, stopping the lathe at intervals to check the tailstock center. After roughing, reverse the ends of the workpiece so that the area held by the lathe dog can be turned. When the piece is within 1/32 to 1/64 inch of the desired size, reduce the depth of cut, reduce the feed,increase the speed, and take light finishing cuts to the proper dimension.Measure the workpiece after each cut, with micrometer calipers. Reverse the piece again and, using shims under the lathe dog to prevent scoring of the machined surface, finish the other end of the workpiece.

 POSITION OF CUTTER BIT FOR STRAIGHT TURNING
POSITION OF CUTTER BIT FOR STRAIGHT TURNING

Author: Aliva Tripathy

Taking out time from a housewife life and contributing to AxiBook is a passion for me. I love doing this and gets mind filled with huge satisfaction with thoughtful feedbacks from you all. Do love caring for others and love sharing knowledge more than this.

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